[OpenBIOS] Ppc guest debugging?

[Mark Cave-Ayland]

On 11/10/2018 12:12, Jd Lyons via OpenBIOS wrote:

>>>> I installed gdb-multiarch and started qemu with:
>>>>
>>>> Qemu-system-ppc -s -S
>>>>
>>>> The launched gdb-multiarch and connected  to port 1234.
>>>>
>>>> Is this the correct toolchain for debugging PPC code on an X86 host, or do I need to do something else?

I actually build gdb from source for the architectures I need (sparc32, sparc64 and
ppc), so I can't really comment on how multi-arch works.

>>> I used Apple's PowerPC gdb.

Note that Apple have patched their gdb quite heavily, for example I couldn't even
build it on Linux. On the plus side if you are able to do this, Apple's gdb is at
least able to read symbols from Mach binaries.

>> My host system is X86, I was thinking Mark, or someone here once outlined a way to debug Openbios by installing some sort of  powerpc debug tools on X86?
>> -- 
> 
> Ok, breakpoint not working with gdb-multiarch:
> 
> (gdb)target remote localhost:1234
> (gdb)break CalcRAMSize
> (gdb)continue
> 
> It just boots the Mac OS and only waits before continue. 
> 
> I'm sure I'm doing something wrong here, maybe I need some PPC Libs installed, my host is X86?

I normally allow gdb to detect correct arch before attaching to the remote with
"target remote ..." by passing a relevant ELF file to gdb e.g.

power-linux-gdb openbios-ppc

Note that symbols such as CalcRAMSize are generally only visible in the guest, so
you'll either need to take the executable from the guest and generate a gdb symbol
file for it, or otherwise use breakpoints for routines based upon their address e.g.

break *0x12345678



ATB,

Mark.